Referenced on p.12 ELI - 58 The Janissaries by David Nicolle and Christa Hook:
One of the earliest reliable illustrations of a Janissary officer's uniform is this drawing by the late 15th century Italian artist Gentile Bellini or by one of his students. (Bellini did visit Istanbul). This officer is still armed with a bow, whereas many Janissary soldiers were already adopting firearms. His quiver is of a cavalry type.
(Inv. 47033/3, British Museum, London).